Modern broilers today have the potential to gain body protein quickly through nutrient intake during starter and grower periods. However, protein deposition requires adequate calorie intake in combination with digestible amino acids for maximum accretion. Research is needed to understand when and how much additional energy intake is needed for maximum protein deposition in order to better design feeding programs for feeding phases. Two studies were conducted to determine the daily dietary energy utilization for protein deposition by using dual energy x-ray absorptiometry (DEXA) (GE Lunar Prodigy). In Exp1, a total of 1440 fast-growing male broilers were randomly assigned to 48 floor pens and fed one of two test diets from d3 to d10 throughout an 8-day experimental period (8 trts; 6 reps). Each treatment consisted of feeding one diet (Diet 1) for a set period of days and then switching the diet to a higher energy diet (Diet 2). Diet 1 was formulated to Cobb500 starter recommendations ( ME 3008 Kcal/kg and 3.92 g dLys/Mcal) while the Diet 2 contained 50 extra kcals ME/kg and a constant protein to energy ratio, similar to the ratio in Diet 1. At d10, broilers were scanned to determine the dietary energy intake needed for maximum protein deposition. In Exp2, a total of 1440 fast-growing male broilers were randomly assigned to 48 floor pens and fed one of two test diets from d9 to d16 throughout an 8-day experimental period (8 trts; 6 reps). Each treatment consisted of feeding one diet (Diet 1) for a set period of days and then switching the diet to a higher energy diet (Diet 2). Diet 1 was formulated to Cobb500 grower recommendations ( ME 3086 Kcal/kg and 3.40 g dLys/Mcal) while the Diet 2 contained 50 extra kcals ME/kg and a constant protein to energy ratio, similar to the ratio in Diet 1. At d17, broilers were scanned to determine the dietary energy intake needed for maximum protein deposition. Data was analyzed one-way ANOVA using JMP Pro 14 (SAS Institute, 2018). Exp1 showed body weight, lean mass, protein mass significantly increased when the diet was changed to a higher energy containing diet on d6 (P<0.05). The results in Exp2 presented that the protein mass significantly increased in the treatment that had diet changes on d16 (P<0.05).
These studies indicate that d6 was the age of broiler required extra energy stimulation with the same amino acid ratio to energy from hatch through d16 and the next broiler age that needed energy stimulation response was d16 with diet stayed the same amino acid ratio to energy. This model would develop accurate phase feeding of broiler diets throughout 42 days in further.
